The present invention relates to a process for preparing 5-arylhydantoins. The 5-arylhydantoins are important compounds as a raw material for preparing D-2-arylglycines such as D-phenylglycine and D-p-hydroxyphenylglycine which are useful for preparing a semisynthesized penicillin or cephalosporins.
The 5-arylhydantoins were, in the old days, prepared from a corresponding aryl aldehyde, ammonium carbonate and sodium cyanide according to Bucherer-Berg method, as discussed in Journal fur Praktische Chemie, 1934, 140, 291. Also, various preparation methods of the 5-arylhydantoins have been known. For instance, Japanese Examined patent Publication No. 55-22474 discloses a method wherein glyoxylic acid, urea and phenol are reacted under an acidic condition. Japanese Examined patent Publication No. 55-16582 discloses a method wherein allantoin is reacted with phenol. Japanese Examined Patent Publication No. 57-57033 discloses a method wherein hydroxymandelic acid is reacted with urea. Japanese Unexamined Patent Publication No. 54-128572 discloses a method wherein glyoxylurea is reacted with phenol. Japanese Unexamined Patent Publication No. 54-138558 discloses a method wherein alloxanic acid is reacted with phenol. Japanese Unexamined patent Publication No. 54-138559 discloses a method wherein diglyoxylic acid triureide is reacted with phenol. Japanese Unexamined Patent Publication No. 54-138560 discloses a method wherein 5-hydroxyhydantoin is reacted with phenol.
According to Bucherer-Berg method, however, it is required to use sodium cyanide which is dangerous. Furthermore, the obtained crude hydantoin is contaminated with a large amount of a by-product or the obtained hydantoin is colored due to the oxidative side reaction of the phenol ring under an alkaline condition. Also, other methods as discussed above are unsatisfactory because the used raw materials, namely, glyoxylic acid, allantoin, hydroxymandelic acid, glyoxylurea, alloxanic acid, diglyoxylic acid triureide and 5-hydroxyhydantoin are expensive.
An object of the present invention is to provide a process for preparing 5-arylhydantoins from an unexpensive raw material, which has no defects as mentioned above.
This and the other objects of the present invention will become apparent from the following description hereinafter.